Re: Equipotential lines

[John Mallinckrodt <ajmallinckro@CSUPOMONA.EDU>]

On Fri, 15 Feb 2002, Ludwik Kowalski wrote:

> ... here is a challenge to those who like to make predictions.
>
> What kind of equipotential lines would you expect for the
> silver strip painted on a carbon-impregnated paper if the
> shape of the strip was an uncurling flat spiral. Suppose the
> length is 100 cm, the DOP between the terminals is 1 V, the
> uniformly distributed resistance of the strip is 1 ohm.cm and
> the angle is 1800 degrees (5 round trips from the grounded
> terminal at the center to the positive terminal at outer end).
> Draw equipotential lines for U=0.5 V and U=0.25 V. Assume that
> the resistance of the carbon paper, (for example ohms/cm^2) is
> 1000 times larger than that of the silver layer. Ludwik
> Kowalski

Here's my entry.

 <http://www.csupomona.edu/~ajm/special/spiral_ep.gif>

You'll see that I ran out of patience at two cycles, changed the
total DOP to "10", totally ignored the specific values of
resistivity, but included representative E-field vectors to
indicate the general character of the field.

Note in particular the dipole like field external to the spiral
and the related existence of a cusp in the equipotential lines
emerging from the interior as they choose which way to head
around the exterior.

John Mallinckrodt      mailto:ajm@csupomona.edu
Cal Poly Pomona          http://www.csupomona.edu/~ajm